Problem 1. (i) Let f be a smooth convex function defined on a convex domain
For any x, y ? Ohm, using the definition of the convexity and directional derivative, show that
f(y) >= f(x) + ?f(x).(y - x) ............................... (1)
(ii) Using (1), show that

(?f(y)- ?f(x))*(y-x) >=0

I've been trying to solve this one for days. I would greatly appreciate any assistance/insight.